Hemolytic Uremic Syndrome

Thrombotic microangiopathy (TMA) was described by Moschcowitz in 1924, and the term hemolytic uremic syndrome (HUS) appeared by 1955 to describe a series of patients with small-vessel renal thrombi, thrombocytopenia, and hemolytic anemia. During the 1970s an association was noted between enteric Escherichia coli infections and HUS, and in 1983 the specific trigger of Shiga toxin–producing E coli (STEC) was recognized. This recognition led to classification of HUS as “diarrhea positive” or “diarrhea negative,” although this terminology is no longer popular. Other secondary forms of HUS are known, including HUS associated with invasive pneumococcal infection, human immunodeficiency virus, systemic lupus erythematosus, or uncommon reactions to medications such as cyclosporine. More recently, the term atypical HUS (aHUS) has been used to describe a rare form of HUS occurring in susceptible individuals, most often from defects in regulation of the alternative pathway of complement, whereas typical HUS largely refers to STEC-HUS or pneumococcal HUS.

In patients with bloody diarrhea, it is imperative that front-line providers understand the importance of testing for STEC. In many parts of the world STEC O157:H7 is the most common pathogen leading to HUS, but it certainly is not the only one as many other organisms besides E coli have been causally implicated with HUS. Testing for STEC is evolving quickly. Stool culture, various assays for the Shiga toxin, and most recently DNA testing of stool are all being used, each method with its own strengths and limitations. The most crucial issue is timeliness because the window of opportunity …